KR101626287B1 - Etching of plastic using acidic solutions containing trivalent manganese - Google Patents

Abstract

A method of producing a solution capable of etching a platable plastic is described. The method comprises the steps of: (a) providing an electrolytic bath to an electrolyte comprising a solution of manganese (II) in a 9 to 15 moles sulfuric acid or phosphoric acid solution; (b) applying an electric current to the electrolytic cell comprising an anode and a cathode; And (c) oxidizing the electrolyte to form manganese (III) ions, wherein the manganese (III) ions comprise forming a metastable sulfate complex. The platable plastic may then be immersed in the metastable sulfate complex for a time to etch the platable substrate prior to subsequent plating steps.

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention [0001] The present invention relates to etching of plastics using an acidic solution containing trivalent manganese,

The present invention generally relates to a method of making plastics for subsequent plating on plastics.

It is well known in the art to metallize a non-conductive substrate (i.e., plastic) for various purposes. Plastic molds are relatively inexpensive to manufacture, and metal plated plastics are used in many fields. For example, metal plated plastics are used for decorative purposes and for manufacturing electronic devices. Examples used for decorative purposes include automotive parts such as trim. Examples used in electronic devices include printed circuits in which metals plated in a selective pattern constitute conductors of a printed circuit board, and metal plated plastics used for EMI shielding. ABS resins are the most commonly plated plastic for decorative purposes, while phenolic and epoxy resins are the most commonly plated plastics for printed circuit board fabrication.

The manufacture of plastics for subsequent plating is a multi-step process, and typical process steps include:

1) etching the substrate with a chromic acid etching solution;

2) neutralizing the etched surface with a chromium neutralizing solution;

3) activating the etched surface with a colloidal palladium tin activator;

4) removing the tin by a promoting step; And

5) depositing a layer of electroless copper or electroless nickel followed by electrolytic copper and / or electrolytic nickel plating.

The initial etching of the plastic substrate is an integral part of the overall process, and essentially all commercial processes use a chromic acid etch solution as the source of hexavalent chromium for the plastic etch step. This process has a number of features. Various plastics, including ABS and ABS / polycarbonate blends, can be plated with excellent plate appearance and adhesion. The immersion time and / or temperature in the chromic acid etch solution can be increased to plate the more difficult plastic containing higher levels of polycarbonate or polypropylene. In addition, extreme hardness plastics that are etch resistant, such as pure polycarbonate, can be plated by incorporating a solvent prior to the chromium etching step.

Only some types of plastic components are suitable for plating, and as discussed above, the most common types of plastics for electroplating are acrylonitrile / butadiene / styrene (ABS) or a blend of the above materials with polycarbonate / PC). The ABS consists of two phases. There is a relatively rigid phase consisting of an acrylonitrile / styrene copolymer and a softer polybutadiene phase. Currently, the material is mostly etched using a mixture of chromic acid and sulfuric acid. This oxidizing acid mixture is very effective as an etchant for ABS and ABS / PC. The polybutadiene phase of the plastic contains double bonds within the polymer backbone, which are oxidized by the chromic acid to completely break and dissolve the polybutadiene phase exposed on the plastic surface, thus achieving effective etching of the plastic surface.

The purpose of the etching step is twofold. First, the plastic is etched to increase the surface area. The second is to make the plastic hydrophilic so that the surface is receptive to subsequent activation and plating stages. Typical chromic acid etch solutions are described, for example, in U.S. Patent No. 4,610,895 to Tubergen et al., U.S. Patent No. 6,645,557 to Joshi, and U.S. Patent No. 3,445,350 to Klinger et al. Which patent documents are incorporated herein by reference in their entirety.

One problem with typical chromic acid etching steps is that chromic acid is an approved carcinogen and that regulation is being strengthened, and in all cases it is compulsory to replace the use of chromic acid with other safer materials. The use of chromic acid etchants also has the disadvantage that they are difficult to dispose of due to the toxicity of the chromium compounds and that the chromic acid residues remain on the polymer surface to inhibit electroless deposition and that the chromic acid residues Which is known to those skilled in the art. In addition, it is natural that high temperature hexavalent chromium sulfate solutions are harmful to workers. Burns and bleeding are common in workers routinely associated with these chromium etching solutions. Thus, it is highly desirable to develop safer alternative materials for acidic chromium etching solutions.

Permanganate solutions are described in U.S. Patent No. 3,625,758 to Stahl et al., Which is incorporated herein by reference in its entirety. Stahl suggests the suitability of chromium and sulfuric acid baths or permanganate solutions for surface preparation.

U.S. Patent No. 4,948,630 to Courduvelis, et al., Which is incorporated herein by reference in its entirety, has an oxidation potential that is higher than the oxidation potential of a permanganate solution to produce manganate ions as permanganate Describes a hot alkaline permanganate solution that additionally contains a material such as sodium hypochlorite that can be oxidized to ions. U.S. Patent No. 5,648,125 to Cane, which is incorporated herein by reference in its entirety, describes the use of an alkaline permanganate solution comprising potassium permanganate and sodium hydroxide, wherein the permanganate The salt solution is maintained at elevated temperature, i.e., about 165 ° F to 200 ° F. US Pat. No. 4,042,729 to Polichette et al., Which is incorporated herein by reference in its entirety, describes an etching solution comprising water, permanganate ion and manganate ion, The molar ratio of manganate ion to permanganate ion is controlled and the pH of the solution is maintained at 11-13.

US Patent No. 5,229,169 to Chao (incorporated herein by reference) discloses a process for depositing a metal layer on the surface of a polycarbonate-ABS resin (or other similar resin) Contacting the surface with an alkaline aqueous solution of a water-soluble permanganate, removing all residues of the manganese compounds by contact with a reducing agent, and contacting the surface with a reducing agent, And depositing an electroless metal layer. The alkaline permanganate generally comprises sodium permanganate or potassium permanganate, and the reducing agent may comprise, for example, a hydroxylamine salt solution.

However, attempts to use permanganates to etch plastics (besides epoxy based printed circuit boards) are not very successful. First, the surface treatment of the plastics is inconsistent, providing excellent adhesion at times under the same processing conditions, and sometimes poor adhesion. Second, permanganate solutions can be unstable, have a short life span and are rapidly degraded into manganese dioxide. In addition, compared to chromium etchants, permanganates are less effective and are not suitable for a wide range of plastics mixtures plated in common metal finishing operations.

These attempts to etch plastics using permanganate ions are incapable of producing etch characteristics comparable to those obtained using chromic acid and also lead to the formation of manganese dioxide sludge with poor stability of the etch solutions.

In addition, other attempts to replace chromium etching have been disclosed in the prior art. Patel et al., US Pat. Nos. 4,941,940, 5,015,329 and 5,049,230, the disclosures of which are hereby incorporated by reference in their entirety, disclose a composition comprising at least one swelling agent and at least one Stage or multi-step process for pre-swelling and etching functionalized polymers such as polycarbonate, using an etching solution that includes dissolution of the solvent in the solution. The prepared substrates are then plated with electroless nickel or electroless copper.

Patel et al., US Pat. No. 5,160,600 (the disclosure of which is hereby incorporated by reference in its entirety) discloses a method of replacing a chromic acid etching solution with an etching solution comprising sulfuric acid and optionally phosphoric acid and / or nitric acid. do. The treated substrate is then immersed in a palladium aqueous suspension.

Regardless of whether the oxidant solution is a hexavalent chromium solution or a permanganate solution, contact with the solution acts to stagnate the catalyst surface by retaining oxidant residues on the surface of the plastic portion, thereby hindering metal deposition and often forming voids ≪ / RTI > Simple water rinsing is generally inadequate to remove the residues and thus the art has relied upon additional steps of contacting the reducing agent solution, but removal of the oxidizing agent involves more chemical reaction than simple reduction. Removal of permanganate residues by reducing agents is described in U.S. Patent No. 4,610,895 to Tubergen and U.S. Patent No. 6,645,557 to Joshi, all of which are mentioned above.

As can be readily seen, a number of etching solutions have been proposed as replacements for chromic acid in the process of making non-conductive substrates for metallization. However, these processes have proved unsatisfactory for a variety of economic, performance and / or environmental reasons and these processes have not achieved commercial success or have not been accepted by the industry as an alternative to chromic acid etching.

It has been noted that permanganate solutions tend to form sludge and cause self-degradation. Under strongly acidic conditions, permanganate ions can react with hydrogen ions to produce manganese (II) ions and water according to the following reaction:

_{^{4MnO 4 - + 12-H +}} → 4Mn 2 + + 6H 2 O + 5O 2 (1)

The manganese (II) ions formed by this reaction can then undergo further reaction with permanganate ions according to the following reaction to form sludge of manganese dioxide:

^{_{2MnO 4 - + 2H 2 O +}} 3Mn 2 + → 5MnO 2 + 4H + (2)

Thus, formulations based on strongly acidic permanganate solutions are inherently unstable, irrespective of whether the permanganate ion is added by the alkali metal salt of the permanganate salt or electrochemically generated in situ. Compared to currently used chromic acid etchants, acidic permanganates are not efficiently used in large commercial applications due to poor chemical stability. The alkaline permanganate etchant is more stable, which is widely used in the printed circuit board industry for etching epoxy based printed circuit boards, but alkaline permanganate is not an effective etchant for plastics such as ABS or ABS / PC. Thus, manganese VII is unlikely to achieve broad commercial acceptance as an etchant for these materials.

Other attempts to etch ABS without the use of chromic acid include the use of electrochemically generated silver (II) or cobalt (III). Over the years, it has been known that certain metals can be anodized into highly oxidizing oxidation states. For example, manganese (II) can be oxidized to a permanganate (manganese VI) and cobalt can be oxidized from cobalt (II) to cobalt (III) .

There is currently no commercially available etchant suitable for plastics based on permanganate (in acid or alkali form) or based on manganese in any other oxidation state, or using other acids or oxidants.

Thus, there is still a need in the art for improved etchants for making plastic substrates for subsequent electroplating that are commercially acceptable without chromic acid.

Summary of the Invention

An object of the present invention is to provide an etching agent for a plastic substrate which does not contain chromic acid.

It is another object of the present invention to provide a commercially acceptable etchant for plastic substrates.

It is a further object of the present invention to provide an etchant for plastic substrates based on manganese ions.

The present invention generally relates to compositions suitable for etching ABS, ABS / PC and other plastics materials, and methods of using the compositions.

In one aspect, the present invention relates generally to a method of making a solution capable of etching a plastic substrate,

Providing an electrolytic cell with an electrolyte comprising manganese (II) solution in moles to 15 moles sulfuric acid or in a phosphoric acid solution;

Applying an electric current to the electrolyzer including an anode and a cathode;

Oxidizing the electrolyte to form manganese (III) ions, wherein the manganese (III) ions form a metastable sulfate complex; And

Treating the plastic substrate among the electrolytes

.

In another aspect, the present invention generally relates to an electrolyte capable of etching a plastic substrate, wherein the electrolyte comprises a manganese (III) solution in a 9 to 15 moles sulfuric acid or phosphoric acid solution.

In one preferred embodiment, the electrolyte composition can be used to etch ABS or ABS / PC at a temperature of 30 to 80 占 폚.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

The present inventors have found that trivalent manganese can be easily produced by electrolysis at a low current density of divalent manganese ions in strong sulfuric acid. More particularly, the inventors have found that solutions of trivalent manganese ions in strongly acidic solutions can etch ABS.

Trivalent manganese is unstable and highly oxidative (standard redox potential for normal hydrogen electrodes is 1.51). In solution, trivalent manganese is very rapidly disproportionated to manganese dioxide and divalent manganese through the following reaction:

_{^{2Mn 3 + + 2H 2 O →}} MnO 2 + Mn 2 + + 4H + (3)

However, in a strong sulfuric acid solution, the trivalent manganese ion becomes metastable to form a sulfate complex of cherry purple / red. The present inventors have found that such sulfate complexes are suitable media for the etching of ABS and have a number of advantages over the chromium-free etchants described above.

In one aspect, the present invention relates generally to a method of making a solution capable of etching a plastic substrate,

Providing an electrolytic bath to an electrolyte comprising manganese (II) ions in a 9 to 15 moles sulfuric acid or phosphoric acid solution;

Applying an electric current to the electrolyzer including an anode and a cathode;

Oxidizing the electrolyte to form manganese (III) ions, wherein the manganese (III) ions form a metastable sulfate complex; And

Treating the plastic substrate with the electrolyte to etch the surface of the plastic substrate;

.

In a preferred embodiment, the plastic substrate comprises ABS or ABS / PC.

Both phosphate and sulfuric acid will be effective in the compositions of the present invention, but in a preferred embodiment, the acid is sulfuric acid. The stability of manganese (III) ions in sulfuric acid and phosphoric acid has been studied. At ambient temperature, the half-life of manganese (III) ions in 7M sulfuric acid is about two years. In contrast, the half life of manganese (III) ions at similar concentrations in 7M phosphoric acid was about 12 days. The much higher stability of manganese (III) ions in sulfuric acid is believed to be due to the formation of manganese-sulfate complexes and the higher concentration of available hydrogen ions in the sulfuric acid solution. A further problem with the use of phosphoric acid is the limited solubility of manganese (III) phosphate. Therefore, although other inorganic acids such as phosphoric acid can be used in the composition of the present invention, it is generally preferable to use sulfuric acid.

The excellent stability of the manganese (III) ions in the strong sulfuric acid provides the following operating advantages:

1) Since the Mn (III) ions are formed at low current densities, the power demand for the process is typically very low.

2) Because the anode operates at a very low current density, a cathodic reduction of Mn (III) ions can be prevented using a cathode that is smaller than the anode area. This eliminates the need for a split electrolytic cell and simplifies the engineering of the etchant regeneration cell.

3) Since the process does not produce permanganate ions, there is no likelihood of producing manganese oxide in the solution (the manganese oxide described above is highly explosive and thus poses a significant safety risk).

4) Because of the high stability of Mn (III) ions in strong sulfuric acid, the etchant can be sold in ready-to-use form. In order to maintain the Mn (III) content of the etchant and prevent the accumulation of Mn (III) ions, the etchant only needs a small regenerative cell on the side of the tank.

5) Because other etching processes are based on permanganate salts, the reaction of permanganate and Mn (II) ions results in fast "sludging" by manganese dioxide and a very short lifetime of the etchant. This would not be a problem in the case of Mn (III) based etchants (there may be some unevenness over time).

6) The electrolytic generation of Mn (III) according to the present invention does not produce any toxic gas. Although some hydrogen may be produced at the cathode, due to the low current requirements, this will be less than the amount produced by multiple plating processes.

As described herein, in a preferred embodiment, the acid is sulfuric acid. The concentration of sulfuric acid may be from about 9 moles to about 15 moles. In this process, the concentration of sulfuric acid is important. At concentrations less than about 9 moles, the etch rate is too slow to be useful, and at concentrations above about 14 moles, the solubility of the manganese ions in the solution is too low to obtain useful concentrations of manganese in solution. In addition, very high concentrations of sulfuric acid tend to absorb moisture from the air and are dangerous to handle. Thus, in a preferred embodiment, the concentration of sulfuric acid is from about 12 moles to 13 moles. This sulfuric acid concentration is sufficiently dilute to allow safe addition of water to the etchant, yet strong enough to optimize the etch rate of the plastic. At this sulfuric acid concentration, about 0.08 M or less manganese sulfate can be dissolved at the desired etching operating temperature. For optimal etching, the concentration of manganese ions in solution must be as high as practicable.

The manganese (II) ions are preferably selected from the group consisting of manganese sulfate, manganese carbonate and manganese hydroxide, but other similar manganese (II) ion sources known in the art will also be useful in the practice of the present invention. The concentration of manganese (II) ions may range from about 0.005 moles to the saturation concentration. In one embodiment, the electrolyte may further comprise colloidal manganese dioxide. This can, to some extent, be formed as a disproportionate natural consequence of manganese (III) in solution, or intentionally added. Methods for making colloidal manganese dioxide are well known in the art.

Manganese (III) ions can conveniently be generated by oxidizing manganese (II) ions by electrochemical means. (III) can be efficiently oxidized to manganese (III) at a current density of 0.1 to 0.4 A / dm 2 when a platinum or platinumated titanium anode is used . At such a current density, the present inventors have found that the conversion efficiency of manganese (II) reaches 100% under the above environment. Further, when a platinumated titanium anode is used at a current density of 0.1 to 0.4 A / dm 2, the anode potential is lower than the oxygen discharge potential, and manganese (III) ions are produced with high efficiency. The present inventors have found that etching of ABS can be achieved by this method.

The electrodes may comprise a material selected from the group consisting of platinum, platinumized titanium, iridium oxide coated titanium, niobium, and other suitable materials. The cathode may also be made of platinum, platinumized titanium, niobium, iridium oxide coated titanium or any other suitable material, preferably platinum or platinumated titanium. The anode can be made of platinumized titanium, platinum, iridium / tantalum oxide, niobium, or any other suitable material, which is preferably platinum or platinized titanium. For efficient generation of manganese (III) ions, it is generally necessary to use a larger anode area than the cathode area. Preferably, the area ratio of the anode to the cathode is at least about 10: 1. Thereby, the cathode can be directly immersed in the electrolyte, so that it is not necessary to have a divided electrolyzer (although this process can also be performed by the divided electrolyzer apparatus, this will cause unnecessary complexity and cost).

In addition, it is generally preferred that the electrolyte not contain any permanganate ions.

In another aspect, the present invention comprises immersing the platable plastic in a metastable sulfate complex for a time to etch the surface of the platable plastic. In one embodiment, the platable plastic is immersed in the solution at a temperature of 30 to 80 占 폚. The etch rate increases with temperature and is very slow at less than 50 ° C. The upper limit of the temperature is determined by the nature of the plastic being etched. ABS begins to deform at temperatures above 70 DEG C, and thus, in a preferred embodiment, the temperature of the electrolyte is maintained at about 50 to about 70 DEG C, especially when etching ABS materials. The immersion time of the plastic in the electrolyte is preferably about 20 minutes to about 30 minutes.

The etched articles in this way may be subsequently electroplated using conventional pretreatment of the plated plastic or the etched surface of the plastic may be used to enhance the adhesion of paint, lacquer or other surface coatings Can be used.

As described in the following examples, the inventors of the present invention found that the concentration of manganese (II) ions used in the etchant of the present invention is diffusion controlled, so that during the electrolytic oxidation process, The need for stirring was revealed by cyclic voltammetry.

In another aspect, the present invention generally relates to an electrolyte capable of etching a platable plastic, wherein the electrolyte comprises a manganese (II) solution in a 9 to 15 moles sulfuric acid or phosphoric acid solution. The electrolyte is oxidized to form manganese (III) ions, wherein the manganese (III) ions form a metastable sulfate complex when sulfuric acid is used.

Now, the present invention will be illustrated through the following non-limiting examples.

Comparative Example 1:

A solution of 0.08 mols of manganese sulfate (500 ml) in 12.5 mols sulfuric acid was heated to 70 占 폚 and one piece of platable grade ABS was immersed in the solution. Even after being immersed in the solution for one hour, there was no discernible etch of the test panel, and upon washing, the surface was not "wetted" and did not maintain an unbroken film of water.

Example  One:

The solution of Comparative Example 1 was electrolyzed by immersing the platinumed titanium anode having an area of 1 dm 2 and the platinumized titanium cathode having a surface area of 0.01 dm 2 in the solution of Comparative Example 1 and applying a current of 200 mA for 5 hours .

During this electrolysis period, the solution was observed to be discolored from almost colorless to very dark purple / red. It was confirmed that no permanganate ions were present.

The solution was then heated to 70 DEG C and one piece of platable grade ABS was immersed in the solution. After 10 minutes of immersion, the test piece was thoroughly wetted and the non-destructed water film was retained after washing. After 20 minutes of immersion, the sample was washed with water, dried and examined using a scanning electron microscope (SEM). The test showed that the test piece was substantially etched and a large number of etch pits were observed with the naked eye.

Example 2:

Test specimens of platable grade ABS were etched at 70 캜 for 30 minutes in the solution prepared as in Example 1. The sample was then washed and plated using the following pretreatment procedure:

1) Treatment in a proprietary preparation (M-neutralize, purchased from MacDermid, Inc.) for plating on plastic

2) Washing

3) Pre-dip in 30% hydrochloric acid < RTI ID = 0.0 >

4) Activation in a propellant palladium colloid activator (D34 C, purchased from McDermid, Inc.)

5) Washing

6) Promotion in the formulations (Macuplex Ultracel 9369, purchased from McDermid, Inc.)

7) Washing

8) Plating in electroless nickel process (Macuplex J64, purchased from McDermid, Inc.)

9) Washing

10) Plating to a thickness of 30 탆 in a copper copper process (CuMac Optima, purchased from McDermid)

In all cases, the process parameters were as recommended in the technical data sheet for each product.

After completing the copper plating process, the sample was dried and inspected. The copper deposit was bright and clear without evidence of blistering and showed good adhesion of the deposit to the substrate.

Example 3:

A solution containing 12.5 M sulfuric acid and 0.08 M manganese (II) sulfate was electrolyzed at a current density of 0.2 A / dm 2 using a plated titanium anode. In order to prevent cathode reduction of the Mn (III) ions generated in the anode, a platinumized titanium cathode having an area of less than 1% of the anode area was used. The electrolysis was long enough to allow a coulomb sufficient to oxidize all manganese (II) ions to manganese (III). The resulting solution was dark cherry purple / red. There were no permanganate ions that occurred during this step. In addition, it was confirmed by visible light spectroscopy that the Mn (III) ions generated an absorption spectrum completely different from the absorption spectrum of the permanganate solution.

Example 4:

The etch solution prepared as described in Example 3 was heated to 65-70 DEG C on a magnetic stirrer / hotplate and test coupons of ABS were immersed in the solution for 20-30 minutes. Some of these test coupons were inspected by SEM and some were normal plated with a plastic pretreatment sequence (reduction in M-neutralization, pre-dipping, activation, acceleration, electroless nickel, copper plating to 25-30 μm) . These test coupons were then annealed and a peel strength test was performed using an Instron instrument.

Peel strength tests performed on coupons plated for 30 minutes exhibited variable peel strength at about 1.5 to 4 N / cm.

Cyclic voltammograms were obtained from a solution containing 12.5 M sulfuric acid and 0.08 M manganese sulfate using a rotating disk electrode (RDE) having a surface area of 0.196 cm 2 at various rotational speeds. A Model 263A potentiostat and a silver / silver chloride reference electrode were used with the RDE.

In all cases, a forward scan showed an increase in current following a peak at about 1.6 V for Ag / AgCl followed by a plateau up to about 1.75 V. A reverse scan produced a similar plateau (at slightly lower current) and a peak at approximately 1.52V. The dependence of these results on electrode rotation speed suggests that mass transport control is a major factor in the mechanism. The platelet represents a potential range when Mn (III) ions are formed by electrochemical oxidation.

Potentiostatic scans were performed at 1.7V. It was observed that the potential dropped initially and then increased over time. The current density at this potential was variable from 0.15 to 0.4 A / dm < 2 >.

After the above experiment, a galvanostatic measurement was performed at a constant current density of 0.3 A / dm 2. Initially, the applied current density was achieved by a potential of about 1.5 V, but as the experiment progressed, a potential increase of about 1.75 V was observed after about 2400 seconds.

The experimental results demonstrate that manganese (III) ions can be generated by electrosynthesis at low current density using platinum or platinumized titanium anodes.

After an etch period of more than 10 minutes, the surfaces of the ABS test coupons were completely wetted and remained non-destructed after the wash. After a period of 20 minutes or 30 minutes, the panels were significantly etched.

Claims (22)

1. A method of producing a solution capable of etching a platable plastic,
Providing an electrolytic cell with an electrolyte comprising manganese (II) ions in a solution of from 9 moles to 15 moles sulfuric acid;
Applying an electric current to the electrolytic cell comprising an anode and a cathode, wherein the anode current density is 0.1 to 0.4 A / dm 2; And
Oxidizing the electrolyte to form manganese (III) ions, wherein the manganese (III) ions form a metastable sulfate complex
≪ / RTI > wherein the platable plastic can be etched. delete The method of claim 1, wherein the sulfuric acid has a concentration of 12 to 13 moles. The method according to claim 1, wherein the manganese (II) ions are selected from the group consisting of manganese sulfate, manganese carbonate and manganese hydroxide. The method of claim 1, wherein said solution is capable of etching platable plastic, further comprising colloidal manganese dioxide. The method of producing a solution according to claim 1, wherein the plating solution is capable of etching a platable plastic in which the concentration of manganese (II) ions in the electrolyte is 0.005 mol to a saturation concentration. The method of claim 1, wherein the cathode comprises a material selected from the group consisting of platinum, platinumized titanium, iridium / tantalum oxide, and niobium. 8. The method of claim 7, wherein the cathode is platinumized titanium or platinum. 2. The method of claim 1, wherein the plating is capable of etching a platable plastic, wherein the area of the anode is larger than the area of the cathode. 10. The method of claim 9, wherein an area ratio of the anode to the cathode is at least 10: 1. delete The method according to claim 1, wherein the temperature of the electrolyte is maintained at 30 占 폚 to 80 占 폚. The method of claim 1, wherein the electrolyte is capable of etching a platable plastic that does not contain any permanganate salt. 3. The method of claim 1, further comprising immersing the platable plastic in the metastable sulfate complex for a time to etch the platable plastic. Way. 15. The method of claim 14, wherein the platable plastic is immersed in the metastable sulfate complex for 20 to 30 minutes. 16. The method of claim 15, wherein the platable plastic is capable of etching a platable plastic comprising acrylonitrile-butadiene-styrene or acrylonitrile-butadiene-styrene / polycarbonate. An electrolyte capable of etching a platable plastic, said electrolyte comprising manganese (III) ions in a 9 to 15 moles sulfuric acid solution, said manganese (III) ions being subjected to electrolysis at an anode current density of 0.1 to 0.4 A / An electrolyte capable of etching a platable plastic. delete 18. The electrolyte according to claim 17, wherein the sulfuric acid has a concentration of 12 to 13 moles. 18. The electrolyte of claim 17, wherein the electrolyte further comprises a colloidal manganese manganese. 18. The electrolyte according to claim 17, wherein the electrolyte does not contain any permanganate salts. The electrolyte according to claim 17, wherein the concentration of manganese (III) ions in the electrolyte is 0.005 mole to a saturation concentration.